(a) Field of the Invention
The present invention relates to new polyols and a process of preparing the same, as well as new urethane elastomers and foams which result from the new polyols. The invention also relates to a process for the preparation of these urethanes. More specifically, the invention is directed to new rigid polyurethane elastomers having a minimum Shore D hardness of 60.
(b) Description of the Prior Art
It is well known to prepare polyols by reacting polycarboxylic acids, their anhydrides or esters (transesterification or polycondensation) with polyhydric alcohols in the presence of a catalyst selected from stannus and stannic chlorides and alkyl-tin compounds. In general, these reactions are carried out at temperatures between about 130.degree. C. and 240.degree. C. for a reaction time which is of the order of 12 to 16 hours.
The reactants used for carrying out this known process include polycarboxylic acids, the anhydrides as well as the esters thereof, and polyhydric alcohols. Among the polycarboxylic acids used, the following are mentioned by way of example: oxalic, malonic, succinic, glutaric, adipic, pimelic, suberic, azelaic, sebacic, brassidic, thapsic, maleic, fumaric, glutaconic, alpha-hydromuconic, beta-hydromuconic, alpha-butyl, alpha-ethylglutaric, alpha-beta-diethyl succinic, isophthalic, terephthalic, hemimellitic and 1,4-cyclohexanedicarboxylic acids.
Among the polyhydric alcohols, a suitable alphatic or aromatic alcohol can be used. By way of example, the following polyalcohols are mentioned:
ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, trimethylene glycol, 1,2-propylene glycol, PA0 1,4-tetramethylene glycol, butylene glycol, 1,2-butylene glycol, PA0 1,4-butane diol, 1,3-butane diol, 1,5-pentane diol, PA0 1,4-pentane diol, 1,3-pentane diol, 1,6-hexane diol, PA0 1,7-heptane diol, glycerol, 1,1,1-trimethylol propane, PA0 1,1,1-trimethylolethane, hexane-1,2,6-triol, neopentylglycol, dibromoneopentylglycol, 1,10-decanediol, PA0 2,2-bis(4-hydroxycyclohexyl)propane, triethylolethane, triethanolamine and pentaerythritol. PA0 Examples include:
This process particularly brings out the use of two steps during the reaction of the acid or the dibasic ester thereof with various polyfonctional alcohols. In the first step, the acid or the dibasic ester reacts with alcohols in which the "hydroxyl" function is only slightly available, such as secondary or tertiary alcohols or primary alcohols which are highly cluttered. Then, more reactive alcohols such as primary alcohols are added to the reaction mixture.
One of the problems encountered during the preparation of ester polyols is the release of water during the polycondensation of dibasic acid with the alcohol: EQU 2R'--OH+HOCO--R--COOH.revreaction.R'OCO--R--COOR'+2H.sub.2 O